fix: clear build directory cache in pytest fixture to avoid stale references

[leemars]

Pull Request Checklist

• A news fragment is added in news/ describing what is new.
• Test cases added for changed code.

Problem

When executing pdm run test tests/cli/test_others.py::test_show_package_on_pypi, the test fails with:

FileNotFoundError: [Errno 2] No such file or directory: '/var/folders/.../pdm-build-xxx/requests-2.32.5-py3-none-any.whl'

Root Cause

The issue occurs when multiple PDM commands are executed sequentially in the same test using the same Core instance:

1. Command 1 (pdm show ipython):

   • create_temp_dir() creates temp directory → stored in _build_dir_cache
   • exit_stack.close() deletes the temp directory
   • Cache still holds reference to deleted directory ❌

2. Command 2 (pdm show requests):

   • Same process, new temp directory created
   • Cache now has reference to two deleted directories

3. Command 3 (pdm show --name requests):

   • Tries to reuse cached directory from Command 1
   • FileNotFoundError - directory no longer exists ❌

The root cause is PreparedCandidate._build_dir_cache (a ClassVar[dict]) persisting across multiple command executions within the same test fixture.

Solution

Clear the cache in the pdm pytest fixture's cleanup phase after exit_stack.close():

if cleanup:
    core.exit_stack.close()
    # Clear the build directory cache to avoid stale references
    from pdm.models.candidates import PreparedCandidate
    PreparedCandidate._build_dir_cache.clear()

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 85.88%. Comparing base (2c93d66) to head (30b8e99).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/pdm/utils.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3743      +/-   ##
==========================================
+ Coverage   85.86%   85.88%   +0.02%     
==========================================
  Files         118      118              
  Lines       12372    12374       +2     
  Branches     2060     2060              
==========================================
+ Hits        10623    10628       +5     
+ Misses       1176     1173       -3     
  Partials      573      573              

Flag	Coverage Δ
unittests	85.74% <66.66%> (+0.01%)	⬆️

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